PoC service is a half-duplex point-to-point or point-to-multipoint speech service based on a mobile network. In a PoC service, a user can start a conversation with the peer end by one keystroke and set up voice and data connections to realize point-to-point or flexible group communications.
PoC service is implemented on the basis of an IP Multimedia Subsystem (IMS) architecture. A terminal that requests PoC service originates a PoC service request to a PoC server. The PoC server controls the rights of joining the conversation, replicates and distributes data packets, and controls point-to-point and point-to-multipoint call; the IMS core provides main functions of an IMS system, including PoC user registration and routing of Session Initiation Protocol (SIP) messages. Routing and triggering of the PoC service are completed in IMS core network elements.
When a terminal communicates via an IMS core network and a PoC server, it must interact with the IMS core network and the PoC server separately when requesting setup of a session. The terminal must go through a complex process when using the PoC service. This gives a bad experience to end users and hinders the applications of the PoC service.